The invention relates to a pipe coupling of glass-fibre reinforced plastics material and a membrane of elastic material which is formed as a seal at least at one end.
From EP 0 651 506 B1 there is known a socket provided with a sealing sleeve for the connection of two plastics pipes, which is developed from a prior art coupling in which the two identically formed part sections each for the receiving of a pipe end are substantially equal in length. The known socket has two significantly different length cylindrical end sections (e.g. preferably with length ratio 1:3 and smaller) and between these is an annular recess in which the sealing sleeve is set. The sealing sleeve has at each end section a sealing lip between which extends a cylindrical section. This is divided by a rib which projects into the interior of the socket into a shorter part adjacent to the longer end region and into a longer part adjacent to the shorter end region.
From U.S. Pat. No. 4,642,156 there is known a method for the manufacture of a sealing sleeve which comprises a stop rib and sealing lips, but no cylindrical section.
It is the object of the invention to provide a pipe coupling which can be used at high pressures, particularly internal pressures of 25 to 50 bar, without causing damage to the coupling by expansion of the pipe as a result of increased internal pressure, and wherein the pipe coupling can be used also with offset and/or angled pipe axes.
A pipe coupling according to the invention comprises a socket of glass-fibre reinforced plastics material and a membrane of elastic material which is formed as a seal at at least one end and comprises a sleeve section. Where the membrane is formed as a seal, at the end of the membrane, where the pipe is to be introduced (i.e. at the outer end), there is a short cylindrical band of the membrane. In the cylindrical band the membrane has a constant wall thickness, which is backed by the glass-fibre reinforced socket material of the pipe coupling.
The pipe coupling of the present invention is suitable for use at high pressures, approximately 15 to 50 bar (depending upon the pipe diameter). With the structure of the pipe coupling provided according to the invention, a reliable connection and sealing of plastics pipes, particularly GFK pipes based on glass-fibre reinforced plastics material, is possible because the short cylindrical band frees the sealing portion from load. Because of the short length of this membrane section, in the event of expansion, i.e. widening of the pipe in diameter, this section expands in the longitudinal direction in response thereto, as a reaction, with the result that the socket is not mechanically stressed by the widening of the pipe. The expansion stroke of the pipe directed towards the socket is thus counterbalanced.
If the cylindrical section is arranged at a small angle, then an angled orientation of a connected pipe is possible. However, a disadvantageous pressure is then exerted on the socket.
Preferably, outside the cylindrical band, the further structure of the pipe coupling is such that an angle is present which is at least as large as the permitted angled orientation of the coupling, and the membrane is anchored in the socket over this angled part. This makes possible the connection of pipes even with longitudinal axes which are offset relative to one another and/or extend at an angle.
Alternatively, only one end may be provided with an angled configuration as mentioned above, with the other end permitting no angled orientation of a pipe. Then, there is basically an angled orientation between pipe and coupling at the one end and at the other end only a telescopic movement of the pipe located in the coupling is possible.
Preferably, the dimensioning of the materials is such that with an internal pressure in the pipe of 1.0xc3x97PN (0.98 bar) up to 1.5xc3x97PN (1.47 bar) the pipe is in contact with the cylindrical band of the pipe coupling without pressure.
At the end where no angled orientation is provided for, the seal can be provided by a ring of elastic material with sealing elements fitted at the forward end of a pipe to be coupled, and the sealing elements effect a seal with the membrane of elastic material of the coupling.
Preferably, the membrane and/or the ring provided with sealing elements is or are of rubber which ensures a particularly reliable sealing against the passage of foreign material.